Method for opening a nip in an extended-nip press and equipment for opening a nip in an extended-nip press

Abstract: The invention concerns a method and an equipment for opening a nip (N) in an extended-nip press. When the nip (N) between the rolls (10, 11) is opened, the loading shoe (12b) of the loading members of the extended-nip roll (11) is shifted to an open position and apart from the glide-belt mantle (F). In the method, the inside end-flange part (20b) of the end flange (20), which is operationally coupled with the bearing means (21) of the glide-belt mantle (F), is rotated as parallel to the face (C) of the central axle (13) of the roll (11), whereby the glide-belt mantle (F) is separated from contact with the back-up roll (10) as the central axis (X₂) of the end-flange part (20b) is placed at a distance (E) from the central axis (X₁) of the roll (11).

Description: The invention concerns an extended-nip press and a method for opening the nip in an extended-nip press according to the preambles of claims 1 and 5, which are based on GB-A-2 182 367. When the back-up roll in an extended-nip press is heated, the press felt and the glide-belt mantle may be damaged if the press has to be stopped out of some reason because of a disturbance in running. For example, when the temperature of the water in a hot-water heated back-up roll is 140°C and the surface temperature is about 80°C during running, after stopping the surface temperature rises to about 120°C. Since the compression of the back-up roll against the closed glide-belt mantle is, as a rule, 20...35 mm, the contact with the back-up roll cannot be removed even if the glide shoe is pulled into the open position. Nor is it possible to displace the back-up roll and the extended-nip roll rapidly into an open position in relation to one another, because, owing to the very high maximal load, the press force is transferred through draw bars or through the frame skeleton. In the present application, an opening method is described in which an eccentric end of the extended-nip press roll is rotated after a movement of opening of the press shoe so that the belt mantle is shifted apart from the back-up roll. In view of avoiding thermal damage to the press felt, the guide rolls of the felt loop may also be displaceable so that the contact of the felt with a hot roll is separated. The method and equipment of opening that are employed herein facilitate replacements of felt and glide-belt mantle and make the replacements quicker. The method in accordance with the invention has the characterizing features of claim 1. The extended-nip press in accordance with the invention has the characterizing features of claim 5. In the extended-nip press according to GB-A-2 182 367 the end pieces to which the glide-belt mantle is attached are radially displacable for e g felt replacement which is a technically more complicated arrangement. The extended-nip press in accordance with the invention comprises an extended nip for a paper or board web. In connection with the lower roll, i.e. the extended-nip press roll, the arrangement of equipment comprises a press member, which can be pressed with a force against the back-up roll, which back-up roll is preferably heated. The back-up roll may also be a non-heated roll. The displaceable press member is preferably a press shoe, which can be pressed with the force of the loading-cylinder means against the heated back-up roll. The press comprises an endless felt H, which is passed through the press zone and which receives water, said felt being arranged to run through the press zone together with the fibrous web W to be dewatered. Further, the press comprises a closed glide-belt mantle of the extended-nip roll, which belt mantle is passed through the press zone, the web being passed through the nip area between the felt and the back-up roll. The press may also comprise two felts, between which the web is carried and pressed. The invention will be described in the following with reference to a preferred embodiment of the invention, which is illustrated in the figures in the accompanying drawings, the invention being, however, not supposed to be confined to said embodiment alone. Figure 1 shows an extended-nip press equipment of a paper machine. Figure 2 shows an assembly of equipment in accordance with the invention viewed in the machine direction. Figure 3 shows one end area of the roll assembly in accordance with the invention as shown in Fig. 2. Figure 4 shows an arrangement of equipment in which the positions of the felt guide rolls and of the blow boxes can be displaced, in which case the felt can also be separated from the heated upper back-up roll. Fig. 1 shows an equipment of an extended-nip press in a paper machine. In the press equipment shown in Fig. 1, the web W is passed into a nip N between a lower extended-nip press roll 11 and a heated back-up roll 10 between the felt H and the roll face 10' of the back-up roll 10. Fig. 2 shows the rolls 10 and 11 of Fig. 1 as viewed in the machine direction. The extended nip between the rolls 10 and 11 is denoted with the reference arrow N in the figure. The felt H and the web W are passed through the nip N. The roll 10 is a heated back-up roll, and the roll 11 is an extended-nip roll, which comprises loading means 12a 1 ,12a 2 ... and in which the loading means 12a 1 ,12a 2 ..., preferably cylinder means, in the central axle 13 are fitted to act with a force upon the loading or glide shoe 12b and further, through the flexible closed glide-belt mantle F, upon the web W to dewater the web. In the present invention, the web W is understood as referring to a paper or board web. The lower extended-nip press roll 11 comprises a flexible closed glide-belt mantle F, which is fitted to run along the face of the loading shoe or glide shoe 12b, an oil medium being passed into the space between the glide shoe 12b and the closed glide-belt mantle F as a lubricating medium. The back-up roll 10 is preferably a roll that is heated by means of an inside heating medium, such as water, steam or oil, or externally, e.g., by means of induction or infrared radiation. The back-up roll 10 may also be a non-heated roll. Fig. 3 shows one side of the rolls 10,11 on an enlarged scale. In the way shown in the figure, the equipment comprises a heated back-up roll 10 and an extended-nip press roll 11 jointly operative with said back-up roll, the paper web W, the felt H, and the glide-belt mantle F of the roll 11 being passed through the nip N between said rolls. The extended-nip press 11 comprises loading means 12, which consist of actuators 12a 1 ,12a 2 ...12a n , preferably of hydraulic cylinders, by whose means the glide shoe 12b is acted upon with a force, being pressed against the back-up roll 10, whereby the web W is subjected to compression between the felt H and the face 10' of the back-up roll 10. The extended-nip press roll 11 comprises a stationary non-revolving central axle 13, which comprises a central-axle portion 13a 1 in the middle and lateral axle portions 13a 2 and 13a 3 of smaller diameter. A flange 13b is formed between the axle portions 13a 1 and 13a 2 . The extended-nip press roll 11 is suspended by means of its central axle 13, by the ends of the axle, on bearing means 14, which permit a certain deflection and angular change for the axle 13 in a loading situation. The bearing housing 15 of the bearing means 14 or the related constructions are coupled with the bearing housing 16 of the bearing means 18 of the roll 10 or with a related construction by means of a tie bar 17 or equivalent. The roll 10 is journalled as revolving by means of bearing means 18. The flange 13b is coupled with one or several actuators 19, preferably cylinder devices, which comprise a cylinder body 19a, a cylinder rod 19b, and, at its end, a roller or a glide piece 19c, which is fitted to run in the groove M in the shoulder 20b' of the end flange 20b. By means of the actuator/actuators 19, the glide-belt mantle F is tensioned by acting upon the end flanges 20 with a force, which end flanges are fitted to glide on the axle portions 13a 2 . The actuator construction 19 may be similar at both ends of the roll. The end flange 20 comprises a first end-flange part 20a and a second end-flange part 20b, which is placed inside the first end-flange part 20a. Between the end-flange parts 20a and 20b, there are journalling means 21 and sealing members 21a. The end-flange part 20b can be made to glide on the axle portion 13a 2 . Thereby, rotation of the end-flange part 20b in relation to the axle 13 is permitted. The bearing means 21 are fitted between the flange parts 20a,20b, and they are held in their positions by means of covers 22a,22b. During operation, the glide-belt mantle F is rotated on bearing means 21. Thus, the end flange 20 is fitted to glide on the face C of the axle portion 13a 2 . The seal 23 is fitted at the side edge of the end-flange part 20b. The seal is fitted to glide against the face C. By means of the actuators 19 the glide-belt mantle F is tensioned between the end flanges 20 in the way described above. The glide-belt mantle F is attached to the end-flange part 20a by means of wedge-ring segments 24 and by means of fastening-ring segments 25 fitted at the outer edge of the end-flange part 20a. The wedge-ring segments 24 are fitted in the fastening-ring segments 25 between the shoulder 26 and the outer face D of the end-flange part 20a. The glide-belt mantle F is tensioned by its ends against the outer face D of the end-flange part 20a by pressing the wedge-ring segments 24 by means of a screw device R tightly towards the bottom of their fastening groove U. In this way, by means of the wedge-ring segments 24, a sealing force is applied to the glide-belt mantle F, and the mantle is kept tightly against the outer face D of the end-flange part 20a. In the way shown in the figure, the axis of rotation and central axis of the outer end-flange part 20a of the end flange 20 in the construction in accordance with the invention is denoted with X 2 . The central axis of the end-flange part 20b is also X 2 . The central axis of the axle 13 of the extended-nip roll 11 is denoted with X 1 . The distance E between the axes X 2 and X 1 is the eccentricity of the end-flange part 20b. The inner flange part 20b of the end flange 20 is rotated around the axis X 1 . According to the invention, in a situation of opening the nip N, the inner end-flange part 20b is rotated by means of an actuator 30 as parallel to the face C of the axle portion 13a 2 of the axle 13, in which case, owing to the difference in distance between the above axes X 1 and X 2 , i.e. owing to the eccentricity E, the glide-belt mantle F is shifted apart from the heated back-up roll 10. The actuator 30 is preferably a hydraulic cylinder, which is provided with articulated joints both at the end of the cylinder rod and at the end of the cylinder body. Fig. 3 includes a sectional view of the piston rod of the cylinder 30. Figure 4 illustrates the arrangement of equipment in accordance with the invention, wherein, in a situation of opening the nip N, the felt H can also be brought apart from the heated back-up roll 10. Separation of the felt H from the back-up roll 10 is necessary especially in extended-nip constructions in which the back-up roll 10 is expressly a heated roll. In the way shown in the figure, the blow box 35 and the felt-guide rolls 40 and 50 are fitted to be displaceable by means of actuators S 1 ,S 2 and S 3 into different positions, downwards as shown n the figure, in which case the felt H can be separated from the back-up roll 10 (Fig. 4 illustrates the actuators). As is shown in Fig. 4, an angle of rotation of about 45° is sufficient for the flange 20b to separate the glide-belt flange from the outer face 10' of the heated roll mantle 10. The actuator 30 is preferably a cylinder device. In Fig. 4, two different operating positions of the cylinder device 30 are illustrated with dashed-dotted lines. In the position Y 1 , the glide-belt mantle F is in the operating position and placed against the roll 10. In the position Y 2 , the end-flange part 20b of the end flange 20 has been rotated through the angle α (about 80°), whereby, owing to the eccentricity E of the end-flange part 20b, the glide-belt mantle F has been shifted apart from the roll 10. For replacement of the press felt H and of the glide-belt mantle F, the extent of opening must be about 20...60 mm. Before said rotation of the end-flange part 20b, the loading shoe 12b has been shifted to the open position, i.e. apart from the glide-belt mantle F, by acting upon the actuators 12a 1 ,12a 2 ...

Claims: Method for opening the nip in an extended-nip press, which extended-nip press comprises an extended-nip press roll (11), a back-up roll (10) cooperating with the extended-nip press roll (11) to form the extended nip and a felt (H) passing through the nip, said extended-nip press roll (11) comprising a non-revolving central axle (13) and loading members (12a 1 , 12a 2 ) connected with the central axle (13), by whose means a loading or glide shoe (12b) is moved towards and away from the back-up roll (10), the extended-nip press roll further comprising a closed flexible glide-belt mantle (F) which is pressed against the back-up roll (10) by means of said glide shoe (12b) and rotatable with respect to the central axle (13) of the roll (11), the glide-belt mantle (F) being attached at its edges to end flanges (20) supported on the central axle (13) of the roll (11), the glide-belt mantle (F) being rotated with respect to the central axle (13) on support of bearings means (21) which are placed between a radially outer part (20a) of the end flanges, to which the glide-belt mantle (F) is attached at its edge and which is operationally coupled with the bearing means (21), and a radially inner part (20b) of the end flanges, the arrangement being such that a paper or board web (W) passed through the nip on support of the felt (H) is pressed against the back-up roll (10) when the glide-belt mantle (F) is made to comply to the shape of the back-up roll (10) by means of the glide shoe (12b) which is acted upon by means of the loading members (12a 1 ,12a 2 ), in which method the nip is opened by shifting the glide shoe (12b) apart from the glide-belt mantle (F) and separating the glide-belt mantle (F) from the back-up roll (10), characterized in that the radially inner part (20b) of the end flange (20), which is operationally coupled with the bearing means (21) of the glide-belt mantle (F), is rotated as parallel to the face (C) of the central axle (13) of the press roll (11), whereby the glide-belt mantle (F) is separated from contact with the back-up roll (10) as the central axis (X 2 ) of said radially inner flange part (20b) is placed at a distance (E) from the central axis (X 1 ) of the central axle (13) of the roll (11). Method as claimed in claim 1, characterized in that, in the method, a separate actuator (30) is used, which is coupled with said radially inner flange part (20b), in which case, when the inner end-flange part (20b) is rotated by means of the actuator (30), the eccentricity (E) of the end-flange part (20b) is utilized and the glide-belt mantle (F) is shifted apart from the back-up roll (10). Method as claimed in any of the preceding claims, characterized in that said radially inner flange part (20b) is rotate by means of a cylinder device (30). Method as claimed in any of the preceding claims, characterized in that, when the nip (N) between the rolls (10,11) is opened, the felt (H) is also shifted apart from the face of the back-up roll (10) by using actuators (S 1 ,S 2 ) and by shifting felt-guide rolls (40,50) for the felt (H) into positions in which they guide the felt (H) so that it is separated from the face of the back-up roll (10), in which case, moreover, a blow-box (35) on the free side of the felt (H), displaced by means of an actuator (S 3 ) so that the blow-box (35) does not stand in the way of the new alignment of the felt (H). Extended-nip press comprising an extended-nip roll (11), a back-up roll (10) cooperating with the extended-nip roll (11) to form an extended nip and a felt (H) passing through the nip, said extended-nip press roll (11) comprising a non-revolving central axle (13) and loading members (12a 1 , 12a 2 ) connected with the central axle (13), by whose means a loading or glide shoe (12b) is moved towards and away from the back-up roll (10), the extended-nip press roll further comprising a closed flexible glide-belt mantle (F) which is pressed against the back-up roll (10) by means of said glide shoe (12b) and rotatable with respect to the central axle (13) of the roll (11), the glide-belt mantle (F) being attached at its edges to end flanges (20) supported on the central axle (13) of the roll (11), the glide-belt mantle (F) being rotated with respect to the central axle (13) on support of bearings (21) which are placed between a radially outer part (20a) of the end flanges (20), to which the glide-belt mantle (F) is attached at its edge, and a radially inner part (20b) of the end flanges (20), the arrangement being such that a paper or board web (W) passed through the nip on support of the felt (H) is pressed against the back-up roll (10) when the glide-belt mantle (F) is made to comply to the shape of the back-up roll (10) by means of the glide shoe (12b) which is acted upon by means of the loading members (12a 1 , 12a 2 ), the extended-nip roll (11) further comprising means for separating the glide-belt mantle (F) from the back-up roll (10) when the glide shoe (12b) is shifted apart from the glide-belt mantle (F), characterized in that said radially inner flange part (20b) is fitted so that its central axis (X 2 ) is placed eccentrically in relation to the central axis (X 1 ) of the axle (13) of the extended-nip press roll (11) and that means for rotating said radially inner flange part (20b) are provided, such that by rotating the end-flange part (20b), the eccentricity (E) of said radially inner flange part (20b) is utilized for shifting of the glide-belt mantle (F) into different positions in relation to the back-up roll (10), apart from the back-up roll or into contact with the back-up roll. Press as claimed in the preceding claim, characterized in that it comprises an actuator (30), which is operationally coupled with said radially inner flange part (20b) for rotating it. Press as claimed in the preceding claim, characterized in that the actuator (30) is a cylinder device. Press as claimed in any of the preceding claims 5 to 7, characterized in that said radially inner flange part (20b) is fitted so that, when it is rotated, it glides along the pheripheral face (C) of a lateral axle portion (13a 2 ) of the central axle (13) of the extended-nip press roll (11). Press as claimed in any of the preceding claims 6 to 8, characterized in that it comprises displaceable guide rolls (40, 50) for the felt (H) at the inlet and outlet sides of the nip (N) as well as a displaceable blow-box (35) on the free side of the felt (H), whereby, by means of actuators (S 1 ,S 2 ,S 3 ), the blow-box (35) and the felt-guide rolls (40,50) can be shifted into positions in which the felt (H) is separated from the contact with the face (10') of the back-up roll (10). Press as claimed in any of the preceding claims 6 to 9, characterized in that the back-up roll (10) is a heated roll.

Inventors: LAAPOTTI JORMA, LAAPOTTI, JORMA
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1994
Main classification: D21F3
IPC codes: D21F3, D21G1